Plug weld holes should be sized as the vehicle maker recommends, or, if no recommendation exists, what size should be used?

Plug weld holes should be sized as the vehicle maker recommends, or, if no recommendation exists, what size should be used?

• A. 8 mm (5/16")
• B. 6 mm (1/4")
• C. 10 mm (3/8")
• D. 12 mm (1/2")

Answer: (A)

Plug weld holes must provide enough weld area to develop the joint’s strength without weakening the base metal. If the vehicle maker specifies a hole size, use that exact size. When there’s no spec, eight millimeters (about 5/16 inch) is a common, safe default because it gives adequate weld metal to resist shear loads while preserving surrounding metal. A smaller hole, like six millimeters, might not furnish enough weld area for a strong joint. Larger holes, such as ten or twelve millimeters, remove more metal and increase the risk of burn-through, distortion, or the need for excessive filler.

Plug weld holes must provide enough weld area to develop the joint’s strength without weakening the base metal. If the vehicle maker specifies a hole size, use that exact size. When there’s no spec, eight millimeters (about 5/16 inch) is a common, safe default because it gives adequate weld metal to resist shear loads while preserving surrounding metal. A smaller hole, like six millimeters, might not furnish enough weld area for a strong joint. Larger holes, such as ten or twelve millimeters, remove more metal and increase the risk of burn-through, distortion, or the need for excessive filler.